Providing a metal layer on a selected area of a surface of an insulating substrate such as a plastic in order to form a passage for transmitting electro-magnetic signals is widely applied in the field of automobile, computer, communications, and so on. The metal layer can be formed on the surface of the insulating substrate such as a plastic in various ways.
There are various methods to form a metal layer on the surface of the insulating substrate such as a plastic, which should be further improved.